Dr. Souvik Das concludes PhD journey with successful defense - congratulations!

Souvik's thesis explores topological materials using STM and STS revealing robust quantum states with potential applications.

Title: “Probing Topological States of Matter using Scanning Tunneling Microscopy and Spectroscopy”

Souvik’s thesis investigates the bulk–boundary correspondence in topological materials using low-temperature Scanning Tunneling Microscopy and Spectroscopy (STM/STS). His work focuses on two distinct systems: a topological crystalline insulator (TCI) and a topological superconductor (TSC). In the TCI Pb_1-xSn_xSe, Souvik demonstrated that a 1D flat band localized at crystal step edges can be engineered to stabilize 1D Stoner ferromagnetism. He also explored a TSC by fabricating a van der Waals heterostructure via molecular beam epitaxy, combining the two-dimensional ferromagnet CrCl₃ with superconducting NbSe₂. The STM/STS measurements revealed an interfacial superconducting state with anomalous robustness against out-of-plane magnetic fields, along with edge modes at the boundaries of CrCl₃ islands. Supported by theory, his findings point to a p-wave topological superconducting state that is stabilized by the Rashba spin–orbit–coupling. Collectively, Souvik‘s work highlights how material engineering can realize exotic quantum states with potential applications in quantum technologies and cryogenic memory devices.